1. Field of the Invention
The present general inventive concept relates to a scanner and an image forming apparatus which can correct a control signal for motor driving using a test image, and a motor control method of the scanner and the image forming apparatus.
2. Description of the Related Art
In general, a scanner reads image information from a document using light. To this end, the scanner includes a sensor unit for reading the image information from the document. The sensor unit has a plurality of sensors arranged in a row for color image scanning.
FIG. 1 illustrates a conventional color sensor unit for color image scanning. Referring to FIG. 1, the sensor unit 10 includes color image sensors 11R, 11G and 11B which are spaced from each other at a predetermined interval ‘p’. Color filters are arranged above the respective color image sensors 11R, 11G and 11B, and receive color images reflected from the document. For example, an original image in an area ‘A’ of a document 1 is separated into a plurality of color images and then image-formed by the image sensors 11R, 11G and 11B. In this way, color data for the area ‘A’ is separately generated and is separately stored in a memory buffer 15.
Then, the color data stored in the memory buffer 15 is combined to realize a scan image 17. In this respect, if a scanning speed is uniform, the plurality of color data read from the same area of the document is spaced from each other at the interval ‘p’ in the memory buffer. Then, the scanned image can be re-formed by relatively moving the color data by the interval ‘p’ to be superimposed.
However, when driving a scan head through a driving part, it is in practice difficult to drive the scan head at a uniform speed. In particularly, in the case that a stepping motor is employed as the driving part, since the stepping motor does not include an encoder, a moving amount of the scan head cannot be fed back, and thus, it is difficult to determine whether or not the scan head moves at a uniform speed.
Due to the above structural features of the driving part, fluctuation in a speed of the scan head occurs, and thereby results in a color registration error in a scanned image.
This problem is caused by the fact that the original image is not directly captured at the same time and color image sensors for extracting color image data are spaced from each other at the interval ‘p’. That is, when the speed of the scan head fluctuates, a relative interval between the color data becomes different from the predetermined interval ‘p’, and thus, the color registration error can occur.
The color registration error may occur in an inkjet image forming apparatus. The inkjet image forming apparatus generally includes a motor and an inkjet head reciprocally moved by the motor to form a color image on a printing medium. The inkjet head includes a plurality of color ink cartridges spaced from each other.
Accordingly, when realizing a full color image by combining inks provided from the color ink cartridges, if the inkjet head is fluctuated, the relative interval between the color data is also fluctuated, to thereby cause the color registration error.